Two-dimensional velocity fields are measured using particle image velocimetry (PIV) at four planes in the near-wake region of a pair of the side wings of a flapping-wing micro air vehicle (MAV) designed at Wright State University. A high-speed camera is used to identify the phases of the flapping motion of the wings. The results emphasize the importance of the coupling between the flexible wings and the flow in future CFD efforts. The results also show that a large-scale vortex ring is shed into the near-wake region during the fling motion of the side wings of the current MAV. The three-dimensional features of this vortex ring are visualized and characterized from the velocity and vorticity fields measured in the four particle image velocimetry planes.